The Clinton camp is reportedly vetting retired four-star Admiral James Stavridis as a potential vice presidential running mate. The former NATO brass served as the DoD’s top adviser during the Iraq War and has speculated on nuclear war with Russia.

Retired Admiral James G. Stavridis, who is now dean of the Fletcher School of Law and Diplomacy at Tufts University, is being considered as a possible running mate by Democratic presidential candidate Hillary Clinton, a source familiar with the matter told the New York Times on Tuesday.

The source said Clinton would probably have “someone with military experience" on her vice-presidential shortlist, and Admiral Stavridis would “fit the description.”

Both Clinton’s staff and Stavridis declined to comment, but Michele Flournoy, a former undersecretary at the Pentagon, told Reuters in a statement that “Admiral Stavridis is one of the finest military officers of his generation.”

“He has the talent, experience, judgment and temperament to serve the American people at the highest levels of our government,” she added. Flournoy herself is said to be a likely Clinton pick for Defense Secretary if the presumptive Democratic nominee wins the presidential race in November.

Admiral Stavridis and Clinton are believed to have close ties, as they headed NATO Supreme Allied Command Europe (SHAPE) and the Department of State, respectively, during Barack Obama’s first term.

“She does the work of two, of 20, of 200 with her energy, with her enthusiasm and with her boundless determination to improve our world,” Stavridis said in 2013 when introducing Clinton at an awards dinner, as quoted by Reuters.

Stavridis played an important role during the controversial Iraq War. From 2002 to 2004, he commanded the Enterprise Carrier Strike Group in the Gulf in support of the US-led invasion of Iraq and, during the first years of the US occupation, he also served as top military adviser to then Defense Secretary Donald Rumsfeld.

In July 2009, he became Supreme Allied Commander Europe (SACEUR), NATO’s top military position, which is traditionally occupied by American senior officers. Three years later, in 2012, he was investigated for using a military aircraft to fly him and his wife to an exclusive winemakers’ party in France.

In May, Stavridis claimed a full-scale nuclear war with Moscow was not unthinkable.

“Under President Putin, Russia has charted a dangerous course that, if it is allowed to continue, may lead inexorably to a clash with NATO. And that will mean a war that could so easily go nuclear,” he wrote in a foreword to 2017 War with Russia, a book by British General Sir Alexander Shireff.

However, a day before the 2016 NATO summit in Warsaw Stavridis, struck a more settled tone, saying, “Building a stable, peaceful and coherent Europe must include Russia.”

Russia’s contribution is critically important to defeating Islamic State (IS, formerly ISIS/ISIL) “just as Russian participation was a key ingredient in stabilizing the Balkans 20 years ago,” the retired Admiral wrote in Huffington Post.

The bloc should engage in “high-level conversation” with Moscow “to reduce military confrontation in the Black, Baltic and Arctic Seas… encourage Russia and Turkey to reduce their acrimony and try to create a larger zone of cooperation with Russia in Afghanistan,” he stressed.

Clinton’s other potential vice presidential picks include Senators Elizabeth Warren of Massachusetts and Tim Kaine of Virginia, according to Reuters.

Meanwhile, Donald Trump’s camp is considering Michael Flynn, a retired US Army Lieutenant General and former director of the Defense Intelligence Agency (DIA), as his Republican running mate.